This invention relates in general to polymers, and in particular to proton conducting polymers suitable for use in fuel cell components, such as polymer electrolyte membranes and electrodes of fuel cells.
Fuel cells are a promising technology for generating electricity with higher efficiency and lower emissions than most current methods. Polymer electrolyte membrane (“PEM”) fuel cells include a proton conducting polymer membrane sandwiched between an anode and a cathode. A fuel such as hydrogen or methanol is flowed into contact with the anode where it dissociates into electrons and protons. The electrons, which cannot pass through the membrane, flow from the anode to the cathode through an external circuit containing an electric load, which consumes the power generated by the cell. On the opposite side of the cell, the cathode adsorbs oxygen from the air, generating a potential that pulls the electrons through the external circuit to give them to the adsorbed oxygen. When an adsorbed oxygen receives two electrons it forms a negatively charged oxygen anion. The polymer electrolyte membrane allows the protons to diffuse through the membrane. When two protons encounter an oxygen anion they join together to form water.
While there has been substantial progress in fuel cells, the barriers that remain for commercialization are significant. In particular, the cost of fuel cells remains high. The most commonly used polymer electrolyte membranes are fluorinated polymer membranes sold under the tradename Nafion® by DuPont, which are sold at a relatively high cost. The fluorinated polymer membranes also have other drawbacks, such as poor durability at high temperatures, susceptibility to contamination by carbon monoxide at normal operating temperatures, methanol crossover in a direct methanol fuel cell, and poor water management characteristics.
Therefore, it would be desirable to provide alternative proton conducting polymers for use in making polymer electrolyte membranes of fuel cells.
In addition to polymer electrolyte membranes, proton conducting polymers can also be used in other fuel cell components. For example, they can be used as binders along with particles of carbon-supported catalyst in the preparation of electrodes for fuel cells. It would be desirable to provide alternative proton conducting polymers for use in making other fuel cell components such as electrodes.